DERMATOPHAGOIDES FARINAE: 141 Adverse Event Reports & Safety Profile

DESCRIPTION Mite extract is a sterile solution containing the extractables of mite whole bodies in 0.25% sodium chloride, 0.125% sodium bicarbonate, 50% glycerol by volume and 0.4% phenol as a preservative. The mites are grown on a medium of yeast and pork and are handled and cleaned in a manner to remove more than 99% of the food medium. The medium contains no material of human origin. This extract may be administered by the scratch, prick-puncture, or intradermal methods of skin testing for diagnostic purposes and subcutaneously for therapeutic purposes as directed under Dosage and Administration. Intradermal skin tests in patients who were puncture test positive (Sum E ≥ 40 mm) to either D. farinae or D. pteronyssinus extract were performed with extracts of the mite food medium obtained from the same supplier. The results, submitted to the FDA by several manufacturers, were as follows: By intradermal testing, there was 1 positive (Sum E ≥ 20 mm) in 44 individuals at an estimated 1% level of medium content (approximately the same as contained in the mite extract). At a ten-fold increase (estimated 10% medium content), 4 positives in 40 individuals were observed. Two of the individuals who were skin test positive to the mite extract and who also were skin test positive to the medium extract were also skin test positive to an extract of yeast (Saccharomyces sp.) when tested by the puncture method. The extract is standardized by comparing its relative potency by ELISA competition to a U.S. reference mite extract available from the Center for Biologics Evaluation and Research, U.S. Food and Drug Administration. The U.S. reference extract has been assigned a potency of 10,000 AU/mL based on quantitative skin testing (1).

AND USAGE Greer Standardized Mite ( Dermatophagoides farinae and/or Dermatophagoides pteronyssinus ) Extracts are allergenic extracts indicated for: skin test diagnosis of mite allergy treatment of patients with mite-induced allergic asthma, rhinitis and conjunctivitis. For immunotherapy, patients must show hypersensitivity to Dermatophagoides farinae ( D. farinae ) or Dermatophagoides pteronyssinus ( D. pteronyssinus ) based on their clinical history, allergen exposure history, and skin test reactivity.

Greer Standardized Mite

Extracts are allergenic extracts indicated for: Diagnosis of skin test reactivity to dust mite allergen (1) Treatment of mite-induced allergic asthma, rhinitis and conjunctivitis in patients that show hypersensitivity to dust mites based on clinical history, allergen exposure history, and skin test reactivity (1)

AND ADMINISTRATION Do not inject intravenously.

Greer Standardized

Mite extracts are diluted with sterile diluent for allergenic extracts when used for intradermal testing or subcutaneous immunotherapy. Dosages vary by mode of administration, and by individual response and tolerance. Parenteral drug products should be inspected visually for particulate matter and discoloration prior to administration, whenever solution and container permit.

Greer Standardized Mite

Extracts should be a light brown solution that is free of particulate matter. If particulate matter is observed then the solution should be discarded.

2.1 Diagnostic Testing For diagnosis of a patient with a suspected allergy to either species of dust mite ( D. farinae or D. pteronyssinus ), diagnostic skin testing should include the standardized mite mixture or the single-species mite extracts. If a skin test with the standardized mite mixture elicits a positive reaction, then the single-species mite extracts can be used to determine the degree of sensitivity to each, and to guide in the selection of extracts and their concentration for immunotherapy, if indicated. A positive skin test reaction to any allergen must be interpreted in light of the patient's history of symptoms, the time of year, and known exposure to environmental allergens.

2.1.1 Percutaneous Skin Testing For percutaneous (scratch, prick, or puncture) testing, use 10,000 Allergy Units/mL Greer Standardized Mite Extract stock concentrate in dropper vials. If patient is suspected of having exquisite sensitivity, such as anaphylaxis, to certain foods and drugs, initiate percutaneous testing with several serial 10-fold dilutions of the usual test concentration. For scratch tests, scarify the skin, and then apply one drop of the extract to the scratch. For prick tests, place one drop of extract on the skin and pierce through the drop into the skin with a slight lifting motion. For puncture tests, place one drop of extract on the skin and pierce through the drop perpendicular to the skin. When using percutaneous test devices, follow the directions provided with the test devices. Include a positive control to detect false negative responses to skin testing, which may occur if serum levels of antihistamines remain from prior medication administration <span class="opacity-50 text-xs">[see Drug Interactions (7.2)]</span>. A glycerinated histamine phosphate diluted to 10 mg/mL (6 mg/mL histamine base) may be used as the positive control. Include a negative control to detect false positive responses, which can occur when the patient has a non-specific reaction to the diluent. A 50% glycerosaline solution may be used as the negative control. Read skin tests 15-20 minutes after exposure. Record the induration (wheal) and erythema (flare) response by noting the longest diameter of each, or by the sum of the longest erythema diameter and the mid-point orthogonal diameters of erythema (ΣE). Percutaneous testing devices often have their own grading systems, as these devices may cause different degrees of trauma to the skin and deliver different volumes of allergenic extract. Follow grading instructions for the device used.

2.1.2 Intradermal Skin Testing Intradermal tests are commonly used when the reaction to percutaneous testing is negative or equivocal but the patient has a strong clinical history of symptoms triggered by exposure to a specific allergen. Because immediate systemic reactions are more common with intradermal testing, prescreening with percutaneous testing is a practical safety measure. 1 Dilute the stock concentrate with sterile diluent. Use saline with human serum albumin (HSA), buffered saline, or saline. If prescreening is not done, or if patients are expected to be high risk, precautions should be observed since some patients have experienced anaphylaxis and death. Patients who do not react to percutaneous skin testing should be tested intradermally at a starting dose of 0.02 to 0.05 mL of a 50 Allergy Units/mL extract dilution. Patients suspected of being highly allergic should first receive a test dose of 0.02 to 0.05 mL of a

0.05 Allergy Units/mL extract dilution. If the initial dose test is negative, subsequent intradermal tests using increasingly stronger doses may be performed up to the maximum recommended strength of 200 Allergy Units/mL. If percutaneous skin testing was not performed, include a positive control to detect false negative responses to skin testing, which may occur if serum levels of antihistamines remain from prior medication administration <span class="opacity-50 text-xs">[see Drug Interactions (7.2)]</span>. A glycerinated histamine phosphate diluted to 0.5 mg/mL (0.18 mg/mL histamine base) or aqueous histamine phosphate 0.275 mg/mL (0.1 mg/mL histamine base) may be used as the positive control. If percutaneous skin testing was not performed, include a negative control to detect false positive responses, which can occur when the patient has a non-specific reaction to the diluent. A 1% glycerin in 0.9% saline solution may be used as the negative control. Measure the wheal-and-flare response after 15-20 minutes, which may be graded using variou methods as described in the instructions for the device used. The mean dose of Greer dust mite allergen required to elicit a positive intradermal test result (ΣE &gt; 50 mm) in a total of 83 mite puncture test positive (ΣE &gt; 20 mm) persons is shown in Table 1.

Table

1.

Intradermal

Reactivity to Mite Allergens Allergen Number of Persons Dose to Elicit 50 mm Sum of Diameter Erythema Reaction Mean (AU*/mL) Range (AU/mL) D. farinae 46 0.00856 0.00004 - 1.75935 D. pteronyssinus 37 0.00570 0.00002 - 1.36341 ** * Allergy Units ** Data is available on file with Greer

2.2 Immunotherapy Subcutaneous injection only. Subcutaneous injections for immunotherapy should be prepared by dilution of stock concentrate based on patient&apos;s reactivity. Stock concentrations of Greer Standardized Mite Extract are available in 5,000 Allergy Units/mL, 10,000 Allergy Units/mL, 30,000 Allergy Units/ mL for immunotherapy.

See Table

2 for dilution preparation. Also see Dosage Modification Guidelines 2.2.1). The initial dose of the extract should be based on the percutaneous test reactivity. In patients who appear to be exquisitely sensitive by history and skin test, the initial dose of the extract should be 0.1 mL of a 0.005 to

0.05 Allergy Units/mL dilution. Patients with lesser sensitivity may be started at a 0.5 to 5 Allergy Units/mL dilution. The dose of allergenic extract is increased at each injection by no more than 50% of the previous dose, and the next increment is governed by the response to the last injection. Large local reactions which persist for longer than 24 hours are generally considered an indication for repeating the previous dose or reducing the dose at the next administration. Any evidence of a systemic reaction is an indication for a significant reduction (at least 75%) in the subsequent dose. Repeated systemic reactions, even of a mild nature, are sufficient reason for the cessation of further attempts to increase the reaction-causing dose. Severe reactions require a decrease in the next dose by at least 50%. Proceed cautiously in subsequent dosing. A maximum tolerated maintenance dose should be selected based on the patient&apos;s clinical response and tolerance. Doses larger than 0.2 mL of the concentrate are rarely administered because an extract in 50% glycerin may cause discomfort upon injection. Since the two mite species tend to cross-react, consider the total Allergy Units content in determining the maximum maintenance dose of the mixture.

2.2.1 Dosage Modifications Guidelines for Immunotherapy The following conditions may indicate a need to withold or reduce the dosage of immunotherapy. In situations prompting dose reduction, once the reduced dose is tolerated, a cautious increase in dosage can be attempted. Immunotherapy should be withheld or reduced in dosage if the following concurrent conditions exist: Severe symptoms of rhinitis and/or asthma; Infection accompanied by fever; or Exposure to excessive amounts of clinically relevant allergen prior to a scheduled injection. Changing to a different lot of extract: All extracts lose potency over time. A fresh extract may have an effective potency that is substantially greater than that of older extracts. Therefore, the first dose from the fresh vial should not exceed a 25% increase of the previous dose or a 75% reduction of the previous dose, assuming both extracts contain comparable amounts of allergen, defined by Allergy Units.

Unscheduled

Gaps between Treatments: Patients may lose tolerance for allergen injections during prolonged periods between doses, thus increasing their risk for an adverse reaction. The duration of tolerance between injections varies from patient to patient. During the build-up phase, when patients receive injections 1 to 2 times per week, it is customary to repeat or even reduce the extract dosage if there has been a substantial time interval between injections. This depends on 1) the concentration of allergen immunotherapy extract that is to be administered, 2) a previous history of systemic reactions, and 3) the degree of variation from the prescribed interval of time, with longer intervals since the last injection leading to greater reductions in the dose to be administered. This suggested approach to dose modification due to unscheduled gaps between treatments during the build-up phase is not based on published evidence. The individual physician should use this or a similar protocol as a standard operating procedure for the specific clinical setting. Similarly, if large unscheduled gaps occur during maintenance therapy, it may be necessary to reduce the dosage. The individual physician should devise a protocol as a standard operating procedure for his or her specific clinical setting in determining how to modify doses of allergen immunotherapy due to unscheduled gaps in treatment. The extract previously used is from another manufacturer: Since manufacturing processes and sources of raw materials differ among manufacturers, the interchangeability of extracts from different manufacturers cannot be assured. The starting dose of the extract from a different manufacturer should be greatly decreased even though the extract is the same formula and dilution. In general, a dose reduction of 50-75% of the previous dose should be adequate, but each situation must be evaluated separately considering the patient's history of sensitivity, tolerance of previous injections, and other factors. Dose intervals should not exceed one week when rebuilding dose. The previous extract has expired or is near expiry: The dating period for allergenic extracts indicates the time that they can be expected to remain potent under ideal storage conditions (2 to 8°C) [see How Supplied/Storage and Handling (16)]. Some loss of potency occurs even when stored under ideal conditions, therefore extracts should not be stored beyond the expiration date. Instead, a new lot of should be used (see "Changing to a different lot of extract", above) Changing from non-stabilized to human serum albumin (HSA) stabilized diluents: Allergenic extracts diluted with HSA and 0.4% phenol are more potent than extracts diluted with diluents that do not contain stabilizers. When switching from a non-stabilized to an HSA stabilized diluent, consider lowering the dose for immunotherapy.

2.2.2 Administration of Immunotherapy Administer immunotherapy by subcutaneous injection in the lateral aspect of the arm or thigh. Avoid injection directly into any blood vessel. The optimal interval between doses of allergenic extract varies among individuals. Injections are usually given 1 or 2 times per week until the maintenance dose is reached, at which time the injection interval is increased to 2, 3, and finally 4 weeks. Because most adverse reactions occur within 30 minutes after injection, patients should be kept under observation for at least 30 minutes. 2 For high risk patients 30 minutes of observation may not be sufficient.

2.3 Dilution Preparation To prepare dilutions for intradermal testing and immunotherapy, start with a 5,000, 10,000, or 30,000 Allergy Units/mL stock concetrate, and prepare a 1:10 dilution by adding 0.5 mL of concentrate to 4.5 mL of sterile aqueous diluent. Subsequent dilutions are made in a similar manner (see Table 2).

Table

2. Ten-fold Dilution Series for Intradermal Testing and Immunotherapy Dilution Extract Diluent AU/mL* AU/mL AU/mL 0 Concentrate 5,000 10,000 30,000 1 0.5 mL Concentrate 4.5 mL 500 1,000 3,000 2 0.5 mL Dilution 1 4.5 mL 50 100 300 3 0.5 mL Dilution 2 4.5 mL 5 10 30 4 0.5 mL Dilution 3 4.5 mL 0.5 1 3 5 0.5 mL Dilution 4 4.5 mL 0.05 0.1 0.3 6 0.5 mL Dilution 5 4.5 mL 0.005 0.01 0.03 * Allergy Units The extracts are diluted with sterile diluents for allergenic extracts when used for intradermal testing or subcutaneous immunotherapy. Dosages vary by mode of administration, and by individual response and tolerance. Administered percutaneouslly for diagnostic testing (2.1); stock concentrate 10,000 Allergy Units/mL (2.1) Administered intradermally for diagnostic testing (2.1); stock concentrate 5,000, 10,000, or 30,000 Allergy Units/mL (2.3) Administered subcutaneously for immunotherapy (2.2); stock concentrate of 5,000, 10,000,or 30, 000 Allergy Units/mL (2.3)

CONTRAINDICATIONS Injections of mite extract should not be administered in the presence of diseases characterized by a bleeding diathesis. Immunotherapy should not be started in patients until a specific diagnosis of Type I allergy to mite is made by a physician based on skin testing with this product. Other contraindications include: EXTREME SENSITIVITY TO MITE: Determined from previous anaphylaxis following skin testing, immunotherapy, or natural exposure. AUTOIMMUNE DISEASE: Individuals with autoimmune disease maybe at risk, due to the possibility of routine immunizations exacerbating symptoms of the underlying disease. MYOCARDIAL INFARCTION: Patients who have experienced a recent myocardial infarction may not be able to tolerate immunotherapy. The benefit-to-risk ratio must be carefully evaluated. CHILDREN WITH NEPHROTIC SYNDROME: Children with nephrotic syndrome require careful consideration and probably should not receive immunotherapy due to a variety of seemingly unrelated events that may cause an exacerbation of nephrotic disease.

ADVERSE REACTIONS Adverse systemic reactions usually occur within minutes and consist primarily of allergic symptoms such as generalized skin erythema, urticaria, pruritus, angioedema, rhinitis, wheezing, laryngeal edema and hypotension. Less commonly, nausea, emesis, abdominal cramps, diarrhea and uterine contractions may occur. Severe reactions may cause shock and loss of consciousness. Fatalities have occurred rarely (11). Systemic reactions occur with varying frequency in different clinics. To some extent, the reaction rate is related to the type and dose of administered extract and to the degree of sensitivity of the patient. Despite all precautions, occasional reactions are unavoidable. Reports from regulatory authorities in Sweden to the Center for Biologics Evaluation and Research (CBER) indicated that several deaths have been associated with the use of mite extracts. CBER was subsequently informed that these deaths may have been related to use by physicians or other health professionals untrained in the administration of potent allergens, rather than a product defect. It should be noted that anaphylaxis and deaths following the injection of mite and other extracts also have been reported by the British Committee on Safety in Medicine in the British Medical Journal, 293:943, 1986. Local reactions consisting of erythema, itching, swelling, tenderness and sometimes pain may occur at the injection site. These reactions may appear within a few minutes to hours and persist for several days. Local cold applications and oral antihistamines may be effective treatment. For marked and prolonged local reactions, steroids may be helpful. The treatment of systemic allergic reactions is somewhat dependent upon the symptom complex. Epinephrine hydrochloride 1:1,000 aqueous, in an adult dose of 0.3 - 0.5 mL (or 0.01 mL per kg. for children) administeredsubcutaneously in the opposite arm is the immediate treatment of choice. A tourniquet should be placed above the site of the extract injection if the injection was done on the extremities. Antihistamines may offer relief of recurrent urticaria, associated skin reactions and gastrointestinal symptoms. Persistent wheezing may necessitate intravenous aminophylline treatment. For profound shock and hypotension, intravenous fluids, vasopressors and oxygen also may be needed. Maintenance of an open airway is critical if upper airway obstruction is present. Corticosteroids may provide benefit if symptoms are prolonged or recurrent.

AND PRECAUTIONS

5.1 Serious Systemic Reactions All concentrates of Greer Standardized Mite Extracts have the ability during skin testing and immunotherapy to elicit serious systemic reactions including anaphylactic shock and death <span class="opacity-50 text-xs">[see Adverse Reactions (6)]</span>. A review of the literature indicates that the incidence of near-fatal reactions to immunotherapy, defined as severe respiratory compromise, hypotension, or both, and requiring emergency treatment with epinephrine, has been estimated as 5.4 events per million injections in a 10-year retrospective survey of allergists. 3 Fatalities from immunotherapy injections have been estimated to occur at a rate of approximately one death per 2.0 to 2.8 million injections in 4-, 10- and 12-year retrospective surveys of allergists. 4-6 Because of the danger of serious reactions, caution is required in testing and treating high risk patients and those with medical conditions that reduce their ability to survive a serious systemic adverse event. High-risk patients are defined as those patients: with labile or steroid-dependent asthma, particularly in those suffering an exacerbation of their symptoms at the time of extract administration; with extreme sensitivity to a particular allergen(s); who are currently using beta blockers; who are receiving an accelerated immunotherapy build-up schedule (e.g., rush immunotherapy); who are being changed from one allergenic extract to another; who are receiving high doses of allergenic extracts. High risk patients have had fatal reactions. In addition, patients not high-risk but on beta blockers have had fatal reactions because beta blockers interfere with beta adrenergics such as epinephrine used in treatment or anaphylaxis. Patients should be kept under observation for a minimum of 30 minutes after receiving allergenic extracts so that any adverse reaction can be observed and properly handled. 2 Medications to treat systemic reactions, as well as emergency equipment should be available for immediate use. Extracts must only be administered by persons who are aware of the risk of systemic reactions, including anaphylaxis; are capable of handling such reactions; and have the necessary drugs and equipment on hand to do so.

5.2 Patients on Beta Blockers Patients receiving beta blockers may be unresponsive to the usual doses of epinephrine used to treat serious systemic reactions, including anaphylaxis. Inhalant allergy immunotherapy should be approached with caution in patients taking beta blockers. The risks of anaphylaxis in these patients should be carefully weighed against the benefits of immunotherapy <span class="opacity-50 text-xs">[see Drug Interactions (7.1)]</span>.

5.3 Autoimmune Disease Immunotherapy should be given cautiously to patients with other immunologic diseases and only if the risk from exposure to the allergen is greater than the risk of exacerbating the underlying disorder. 2 All concentrates of Greer Standardized Mite Extracts can cause serious systemic reactions of varying degrees of severity, including anaphylactic shock and death, particularly in patients: With labile or steroid-dependent asthma (5.1) With extreme sensitivity to allergen(s) (5.1) Who are currently using beta blockers (5.2) Who are on an accelerated immunotherapy build-up schedule (5.1) Who are being changed from one allergenic extract to another (5.1) Who are receiving high doses of allergen extracts (5.1)

PRECAUTIONS GENERAL: This product should not be injected intravenously. The risk of severe allergic reactions can be minimized by taking a careful history and by the use of scratch or prick-puncture testing prior to intradermal testing. If the scratch or prick-puncture test is negative, an intradermal test with a one hundred-fold dilution of the concentration used for scratch or prick tests usually is safe. If there is a history of unusual sensitivity or if the scratch or prick-puncture test is not performed first, a more dilute solution such as 1:10,000 v/v of the concentrate should be used initially for intradermal testing. Systemic allergic reactions may occur as a result of immunotherapy. The risk can be minimized by adherence to a careful injection schedule, which starts with a low concentration of extract and is increased slowly. The physician must be prepared to treat anaphylaxis should it occur and have the necessary drugs and equipment on hand to do so. Extracts should not be administered by the patient or other individuals who are not prepared to treat anaphylaxis should it occur. A separate sterile tuberculin syringe graduated in 0.01 mL should be used for each injection. Antihistamines and hydroxyzine can significantly inhibit the immediate skin test reaction (see DRUG INTERACTION). INFORMATION FOR PATIENTS: Because most serious reactions following the administration of allergenic extracts occur within 20 minutes of the injection, the patient should remain under observation for this period of time. The size of the local reaction should be recorded, because increasingly large local reactions may precede a subsequent systemic reaction with increasing dosage. The patient should be instructed to report any unusual reactions to the attention of the physician. In particular, this includes swelling and/or tenderness at the injection site or reactions such as rhinorrhea, sneezing, coughing, wheezing, shortness of breath, nausea, dizziness or faintness. Caution should be exercised in testing or treating pregnant females because a systemic reaction might conceivably cause uterine muscle contractions leading to abortion. CARCINOGENESIS, MUTAGENESIS, IMPAIRMENT OF FERTILITY: Long term studies in animals have not been conducted with allergenic extracts to determine their potential for carcinogenicity, mutagenicity or impairment of fertility. PREGNANCY CATEGORY C: Animal reproduction studies have not been conducted with mite extract. It is also not known whether mite extract can cause fetal harm when administered to a pregnant woman or can affect reproduction capacity. Mite extract should be given to a pregnant woman only if clearly needed. NURSING MOTHERS: It is not known whether allergenic extracts are excreted in human milk. Because many drugs are excreted in human milk caution should be exercised when allergenic extracts are administered to a nursing woman. PEDIATRIC USE: Although standardized mite extract has not been studied in children, unstandardized extract of D. farinae has been administered by the prick test to asthmatic children ages 1 to 16 without any reported adverse response (6). Extract of D. pteronyssinus has been given subcutaneously for hyposensitization to children ages 5 to 14 with adverse reactions being limited to local discomfort, redness and swelling for one or two days (7). DRUG INTERACTION: Antihistamines and hydroxyzine can inhibit the immediate skin test reaction. Patients being treated with delayed absorption antihistamine tablets should be free of such medication for 48 hours before testing. Non-sedating antihistamines, such as terfinadine and astemizole, may variably suppress the skin response for longer periods of time. Epinephrine injection inhibits the immediate skin test reaction for several hours. Beta-blocking drugs may make patients refractory to the usual dose of epinephrine, in the event epinephrine is required to treat an adverse allergic reaction.

INTERACTIONS

7.1 Beta Adrenergic Drugs Patients receiving beta blocker drugs may not be responsive to beta adrenergic drugs used to treat anaphylaxis 10 , and may wish to temporarily postpone treatment day of skin testing. All such decisions should be made in consultation with the physician <span class="opacity-50 text-xs">[see Warnings and Precautions (5.2)]</span>.

7.2 Antihistamines 1 Skin testing with allergenic extracts should not be performed within 2-3 days of first-generation H 1 -histamine receptor blockers (e.g., clemastine, diphenhydramine) and within 3 to 10 days of second-generation antihistamines (e.g., loratadine, terfenadine), except for astemizole, which requires an interval of 30-60 days between allergenic extract exposure and use. These products suppress histamine skin test reactions and could mask a positive response.

7.3 Topical Corticosteroids and Topical Anesthetics 1 Topical corticosteroids may suppress skin reactivity and should be discontinued at the skin test site for at least 2-3 weeks before skin testing. Topical local anesthetics may suppress flare responses and should be avoided at skin test sites.

7.4 Tricyclic Antidepressants 1 Tricyclic antidepressants can have potent antihistamine effects and will affect skin testing. Since use of tricyclics may alter skin test results, dosing for both skin testing and immunotherapy should be done with caution. If tricyclic medication has been recently discontinued, allow 7-14 days prior to skin testing to obviate the antihistamine effect. The risk of anaphylaxis in these patients should be carefully weighed against the risks and benefits of stopping tricyclics.

7.5 Other Drugs The suppressive action of other drugs should be considered and emphasizes the need for a histamine positive-control test. Patients who are receiving beta agonists may be unresponsive to the usual doses of epinephrine used to treat serious systemic reactions, including anaphylaxis (7.1) Patients should discontinue medications known to suppress the histamine response prior to skin testing including: antihistamines (7.2), tricyclics (7.4), and topical corticosteroids and topical anesthetics (7.3)